This invention relates to methods and devices enabling contraceptive advice to be provided during the human ovulation cycle.
Devices are already commercially available which purport to provide the user with contraceptive advice. Generally these are based on the measurement of basal body temperature, and require the user to make daily measurements. The reliability of the contraceptive advice provided by such devices is questionable.
Devices are also available which measure the concentration of urinary lutenising hormone (LH), and alert the user to the LH surge indicative of ovulation, as an aid to conception.
Although the absolute urinary concentration value of LH varies from one individual to another, and from one cycle to another, the LH surge is such a pronounced event that for practical purposes a urinary LH concentration of 20 mIU/ml can be regarded as a universal threshold indicative of the LH surge under virtually all circumstances.
Although the LH surge is a clearly measurable event, it has not hitherto been regarded as an acceptable indicator for contraceptive purposes because it occurs such a short while prior to actual ovulation. Practical contraceptive advice, which would allow a user to avoid conception by abstaining from unprotected intercourse (ie. without resort to any physical or hormonal contraceptive technique) for a minimal portion of the normal ovulation cycle, has not been considered possible if based solely on the measurement of urinary LH concentration.
The expression xe2x80x9cLH surgexe2x80x9d is used herein to mean the dramatic rise in LH concentration that precedes the event of ovulation. In the art, reference is made also to xe2x80x9cLH maxxe2x80x9d, i.e. the peak concentration of LH. In the majority of individuals, these are for all practical purposes simultaneous, when the cycle is monitored on a day-by-day basis. However, in a few individuals, perhaps 20% of the population, the actual peak concentration of LH is not observed until the day following the main concentration rise. For the purposes of the invention, we prefer to use the observable rise as the critical parameter.
By the invention we have found that, contrary to such expectation, reliable contraceptive advice can be derived simply from the measurement of urinary LH concentration if such measurement is linked to a critical xe2x80x98calenderxe2x80x99 provided for the user.
Previously proposed contraceptive methods based on urinary component analysis have tended to require extensive daily urine sampling and testing, often throughout the entire cycle. Other methods have tended to require an unduly prolonged period of abstinence from unprotected intercourse. The invention achieves a reasonable balance by enabling the testing period and abstinence period to be reduced while providing a worthwhile degree of certainty in the contraceptive advice to the user, and employs techniques that can readily be applied in the home.
The invention provides a method of reducing the likelihood of conception during the human ovulation cycle, wherein commencing on a predetermined day in the interval from numerical day 5 to numerical day 15 inclusive following the onset of menses, frequent (preferably daily) testing of urinary lutenising hormone (LH) concentration is performed until the LH surge associated with ovulation is detected, and unprotected intercourse is avoided during a time interval commencing on or before the first day of urinary LH concentration testing and ending at least 2 days, preferably at least 3 days, following the day of LH surge detection.
The predetermined day on which LH testing should be started can be indicated to the user in instructions associated with an appropriate test kit. The starting day should be sufficiently in advance of a likely ovulation day in a typical cycle, to provide a reasonable xe2x80x9csafexe2x80x9d period during initial use of the method of the invention.
Preferably, at least during an initial usage cycle, commencement of testing is begun not more than 8 days, more preferably not more than 7 days, following the onset of menses.
Preferably, at least during an initial usage cycle, avoidance of unprotected intercourse is begun not more than 8 days, more preferably not more than 7 days, following the onset of menses.
The invention also provides a test kit for providing awareness of the status of the human ovulation cycle, comprising a plurality of disposable urinary LH concentration testing devices together with means enabling a user to record the results of frequent (eg. daily) urinary LH tests and to alert the user to the likelihood of conception occurring, characterised in that the recording/alerting means (and/or instructions associated therewith) advises the user to commence testing on a predetermined day in the time interval from numerical day 5 to numerical day inclusive 15 following the onset of menses and to abstain after the predetermined day from unprotected intercourse until at least 2 days have elapsed following the day of detection of the LH surge.
Preferably, the recording/alerting means (and/or instructions associated therewith) advises the user to commence testing in the subsequent cycle on a numerical day that is at least 4 but not more than 8 days in advance of the numerical day corresponding to the day of detected LH surge in the current cycle. Preferably, the user is advised to abstain from unprotected intercourse until at least 3 days have elapsed following the detection of the LH surge.
The recording alerting means can, for example, be a chart on which the user enters the results of the daily testing, commencing on a predetermined day following the onset of menses. If desired, the chart can be provided with a slidable overlay or cursor indicating an appropriate time interval in accordance with the invention, incorporating for example a marker that the user can locate adjacent on an identified day of LH surge and which can then indicate the end of the xe2x80x9cunsafexe2x80x9d interval. As a preferred feature, the cursor can enable the user to adapt the method of the invention to modify and preferably reduce the number of test days in the subsequent cycle. This can be achieved if the cursor accommodates means to advise the user of an optimum test starting day to be used in the subsequent cycle in advance of the expected day of LH surge detection. In order to provide an adequate xe2x80x9csafexe2x80x9d interval and to accommodate normal variations that are likely to occur between one cycle and another in the same individual, the revised test starting day should be set as a defined number of days in advance of the day of observed LH surge in the current cycle.
Preferably, the recording chart on which daily urinary LH concentrations can be recorded during the course of an ovulation cycle is provided with a cursor that can highlight a group of consecutive xe2x80x9cdaysxe2x80x9d on the chart and which cursor, by alignment with a xe2x80x9cdayxe2x80x9d on which the LH surge detection is recorded, can advise the user of the residual unsafe period during the current cycle. More preferably, the cursor can advise the user to commence urinary LH concentration testing on a predetermined numerical day in the subsequent cycle during the interval of at least 4 but not more than 8 days inclusive in advance of the numerical day of LH surge detection in the current cycle.
The chart can be made re-useable, but preferably is disposable and a new chart is supplied with a plurality of assay devices sufficient for testing during a single cycle.
Alternatively, the recording/alerting means can be an electronic device, such as an electronic monitor, e.g. a micro-processor controlled device, into which the daily test results are entered, e.g. by means of an automatic reader of a sampling device, and which can calculate the calender for the user.
Another aspect of the invention is a disposable urinary LH concentration testing advice when used as part of a test kit as defined above, comprising a reagent-impregnated immunochromatographic assay strip incorporating an anti-LH antibody labelled with a particulate direct label, such as a dye sol, gold sol, or coloured latex particles, the device having a urinary LH concentration sensitivity sufficient to provide to the user a clear test result indicative of the onset of the LH surge. Preferably the assay sensitivity is such that a clear indication is given to the user when the urinary LH concentration rises to a level in the range 20-30 mIU/ml. Suitable testing devices are described in detail in patent specifications GB-A-2204398 and EP-A-383619, the disclosures of which are incorporated herein by reference.
The selection of the appropriate calender is critical to the success of the invention. If commencement of LH testing is too early, an unduly prolonged period of abstinence from unprotected intercourse will be recommended to the user and an essential objective of the invention will be negated. Following identification of the LH surge, the user should be advised promptly of the resumption of the xe2x80x98safexe2x80x99 period.
Although there is much reported experimental work in the scientific literature on the changing urinary hormone metabolite profiles during the human ovulation cycle, we believe that the present invention constitutes the first practical use of a knowledge of the LH profile alone adapted to a simple but constructive means for alerting the user to the status of her current ovulation cycle for the primary purpose of contraception, and which is sufficiently reliable for home use. The literature does not suggest the LH measurement alone could provide sufficiently reliable contraceptive advice, especially under home-use circumstances. Rather, the thinking in the art has been that multiple factors need to be measured and correlated to provide reliable contraceptive advice, even under sophisticated laboratory circumstances.